1. Field of the Invention
The invention relates to a turn indicator unit, more particularly to a turn indicator unit for a relay-controlled flasher.
2. Description of the Related Art
Referring to FIG. 1, a conventional turn indicator for indicating the direction in which a vehicle (not shown) is about to turn includes a pair of lamps 22, 23, each of which is connected across an output side 211, 212 of a relay-controlled automotive flasher 21.
In operation, when both lamps 22, 23 are operational, the load resistance across the output side 211, 212 of the automotive flasher 21 is equal to the equivalent resistances of the individual lamps 22, 23 in parallel. The automotive flasher 21 operates such that each of the lamps 22, 23 flashes in the 1 to 2 Hz frequency range. When the lamp 22 fails, the load resistance across the output side 211, 212 of the automotive flasher 21 is equal to the equivalent resistance of the lamp 23. In this case, the automotive flasher 21 operates such that the lamp 23 flashes in the 3 to 5 Hz frequency range, which serves as an indication for the vehicle owner to conduct replacement of the lamps 22.
When it is desired to replace the lamp 22 of the conventional turn indicator with a high resistance lamp (not shown), such as a light-emitting diode lamp, a resistor 24 is coupled across the light-emitting diode lamp. It is noted that, without the resistor 24, which serves as an impedance matching component, since the light-emitting diode lamp has a equivalent resistance that is relatively large when compared with that of the lamp 22, the automotive flasher 21 operates such that each of the lamp 23 and the light-emitting diode lamp does not flash in the required 1 to 2 Hz frequency range. The resistor 24, however, consumes a relatively large amount of power and introduces heat dissipation problems.